1. Field of the Invention
The invention relates to a record carrier comprising a servo track indicating an information track intended for recording information blocks represented by marks having lengths expressed in channel bits, the servo track having a periodic variation of a physical parameter, this periodic variation being modulated for encoding record carrier information.
The invention further relates to recording and/or playback device comprising means for writing and/or reading information blocks represented by marks having lengths expressed in channel bits in an information track on the record carrier, and means for scanning the servo track and retrieving the record carrier information.
The invention further relates to a method for manufacturing the record carrier.
2. Description of the Related Art
A record carrier and device of the type defined in the opening paragraph, for reading and/or writing information, are known from International Patent Application No. WO 00/43996, corresponding to U.S. Pat. No. 6,765,861 (PHN 17323). The information is encoded into an information signal which includes time codes and may be subdivided in accordance with this time codes into information blocks, the time codes being used as addresses, such as, with CD-ROM or DVD+RW. The record carrier has a servo track, usually called a pre-groove, for causing servo signals to be generated when scanning the track. A physical parameter, e.g., the radial position, of the pre-groove periodically varies constituting a so-called wobble. During the scanning of the track, this wobble leads to a variation of the servo signals. The variation is modulated by record carrier information, e.g., synchronization symbols and encoded position information, this position information indicating the absolute length of the track from the start. During recording, the position of the information blocks is synchronized as much as possible with the synchronization symbols, so that the information blocks are written on the record carrier at a position corresponding to their addresses.
A problem of the known system is that the pre-groove wobble signal cannot be demodulated reliably for recovering the encoded position information.